Jack-screw



(No Model.) I

K scu No. 514,091. Patented Feb. 6, 1894.

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I Urtrrsn STATES .PATENT @rrrcs.

JOHN D. LYNCH, OF MONTAGUE, ASSIGNOR TO THE MILLERS FALLS COM- PANY, OF MILLERS FALLS, MASSACHUSETTS.

JACK-SCREW.

SPECIFICATION forming part of Letters Patent No. 514,091, dated February 6, 1894.

Application filed October 21, 1893. S i l No. 4.88.818. (No model.)

To all whom it may concern.-

Beit known that I, JOHN D. LYNCH, of Montague, in the county of Franklin and State of Massachusetts, have invented a new and useful Improvement in Jack-Screws, of which the following, taken in connection with the accompanying drawings, is a specification.

Like letters of reference indicate corresponding parts.

Figure 1, is a sectional elevation on the line no, a: of Fig. 2. Fig. 2, is a plan View of the top of the jack screw, with the top bearing plate removed. Fig. 3, represents one of the separating wedges. Fig. 4., represents one of the rollers.

This invention relates to jack screws used for elevating buildings, cars, &c. The particular part of the article to which this inventlon more especially appertains is the upper end; the object being to so construct the bearing plate in its frictional contact with the upper end of the head of the screw that more weight can be raised by the same exercise of power applied in turning the screw.

vters.

In the-drawings B. is the head of the screw part of the ordinary jack screw. This article is so well known that a general description only will be necessary. The ordinary form consists of a base part provided with a nut into which a screw threaded to work in the nut works. By turning the screw it will of course be raised or lowered in relation to the base part. The screw is attached to the head B. in the ordinary manner and the working of the screw in the nut fixed in the base is the same as usual.

G. represents the usual hole made through the screw head, into which a bar is inserted for a lever to turn the screw. The top of the screw head in my invention is formed as shown, with a central round tenon b. with screw hole e. into which hole the screw E, en-

Around the tenon' b. is formed a fiat table (1. Upon this table are placed several small metal rolls, 0. while between each of the rolls 0. is placed a movable wedge shaped piece of metal D.

The bearing plate or cap piece A. is formed to journal on tenon I). while the lower part is cut out internally to permit room for the rolls and wedges, as shown in Fig. 1, the face g.

of the bearing plate resting upon the top of the rolls 0. The side of the bearing plate preferably extends down andoverlaps the table d. and serves to keep the rolls and wedges in position and also to exclude dirt. The bearing plate being placed over tenon b. the face g. resting on top of rolls 0. placed around the tenon b. on table d. is held in position by the cap piece F'. and screw E. Room is left so that any wear may be taken up or compensated for by inserting the screw E. more or less in hole e.

The operation is very simple. The jack being placed under the object to be raised, the said object resting on the top of bearing plate A. a bar is inserted in hole G. and the screw turned up. Heretofore the bearing plate A. has been simply journaled on the head of the screw and the friction in raising a great weight has been considerable. By my device the friction is reduced very greatly and only a fraction of the power is required to raise a given weight. Of course,I can thus do more work with the same jack and with greater speed and less power applied to the lever; there is also less strain upon the jack.

On account of the great weight to be raised, I have found no other form of anti-frictional device is effective; for instance balls in place of rolls would not answer as they present too small a bearing surface and would quickly become unserviceable. By combining the rolls with my conical wedge shaped pieces D. I am enabled to obtain a most astonishing result. I do not desire to confine myself to the precise form of parts shown as they may be varied somewhat and still be within the spirit of my invention; for instance, the wedges D. might be fixed instead of movable, and the rolls might be pivoted to the tenon b. but they would not work as well or do as much work.

Having now described my invention, what I claim, and desire to secure by Letters Patent of the United States, is-- 1. In a jack screw, the screw head B. provided with the bearing table 01. and the central tenon 5.; the bearing plate A. formed to journal on the tenon b. and having a recess in the under side for the reception of rolls, with the bearing face g.; the rolls 0. independent of each other and adapted to rest movable wedge shaped blocks D. the said rolls and the said blocks independently supported 15 upon a bearing table formed on the head of the screw, and adapted to operate substantially as and for the purposes set forth.

In testimony whereof I have signed my name to this specification, in the presence of 20 two subscribing witnesses, on this 9th day of October, A. D. 1893.

JOHN D. LYNCH. Witnesses:

GEO. E. ROGERS, GEO. W. NIMs. 

